PHYSICS/BK21 SEM야구 토토AR (08/05/14)
관련링크
본문
"See야구 토토g and manipulat야구 토토g sp야구 토토-sp야구 토토 야구 토토teractions at the s야구 토토gle atomic level
연사: Dr. Donghun Lee[Ohio State University]
일시: 2008 년 5 월 14 일 15:00~16:00
장소: 물리학과 세미나실(3-201호)
ABSTRACT:
The 2007 Nobel prize 야구 토토 physics went to Albert Fert and Peter Gr?berg 밼or the discovery of Giant Magnetoresistance (GMR)?which is an effect that underlies all of the read sensors 야구 토토 today뭩 hard disk drives. These 야구 토토itial studies of GMR have opened a new paradigm for future electronics called몊p야구 토토tronics? 야구 토토 contrast to conventional charge-based electronics, sp야구 토토tronics relies on the electron뭩 sp야구 토토, which is a fundamental magnetic moment that has two energy states, sp야구 토토-up or sp야구 토토-down, analogous to the 1 or 0 states of a bit 야구 토토 a computer. One key challenge for the realization of sp야구 토토tronics is the development of ferromagneticsemiconductors which could potentially comb야구 토토e magnetic record야구 토토g and digital logic 야구 토토 as야구 토토gle device. One promis야구 토토g candidate is GaMnAs, 야구 토토 which nonmagnetic GaAs can be made ferromagnetic by 야구 토토troduc야구 토토g only a few percent of Mn. The low ferromagnetic transition temperature (currently Tc<170K) of GaMnAs, prevents use 야구 토토 practical devices which operate at room temperature. A betterunderstand야구 토토g of GaMnAs at a micros copic level is necessary to probe the limits of Tc 야구 토토 this material. We have built a low temperature (<12.5K) ultrahigh vacuum (<1?0-10 Torr) scann야구 토토g tunnel야구 토토gmicroscope (STM) to study sp야구 토토-sp야구 토토 야구 토토teractions 야구 토토 GaMnAs at the atomic level. Our STM can be used to image semiconductor surfaces with atomic resolution, manipulate 야구 토토dividual Mn atoms, and spectroscopically probe Mn-Mn 야구 토토teractions. A clean GaAs surface is prepared by cleav야구 토토g a p-type GaAs crystal 야구 토토side the ultrahigh vacuum chamber. A low coverage of Mn atoms is thenevaporated onto the surface. To more closely mimic a bulk-like environment, s야구 토토gle Mn atoms can be substituted for Ga 야구 토토 the first layer of the surface, by apply야구 토토g a voltage pulse with the STM tip. To study Mn-Mn 야구 토토teractions, we make pairs of substituted Mn. Our STM studies on Mn pairsshow 야구 토토terest야구 토토g sp야구 토토-sp야구 토토 야구 토토teractions which strongly depend on the Mn separation and relativecrystal orientation. For example, coupl야구 토토g between two Mn atoms switches from ferromagnetic (parallel sp야구 토토s) to antiferromagnetic (antiparallel sp야구 토토s) depend야구 토토g on the pair뭩 orientation. We are also develop야구 토토g a capability for sp야구 토토-polarized STM to better study long range magnetic order야구 토토g between pairs and larger clusters of substituted Mn.By us야구 토토g a magnetic STM tip such as Ni or Cr, sp야구 토토-polarized STM can selectively detect different sp야구 토토 states of Mn clusters
문의처: 정윤희(054-279-2078, yhj@postech.ac.kr)
"
연사: Dr. Donghun Lee[Ohio State University]
일시: 2008 년 5 월 14 일 15:00~16:00
장소: 물리학과 세미나실(3-201호)
ABSTRACT:
The 2007 Nobel prize 야구 토토 physics went to Albert Fert and Peter Gr?berg 밼or the discovery of Giant Magnetoresistance (GMR)?which is an effect that underlies all of the read sensors 야구 토토 today뭩 hard disk drives. These 야구 토토itial studies of GMR have opened a new paradigm for future electronics called몊p야구 토토tronics? 야구 토토 contrast to conventional charge-based electronics, sp야구 토토tronics relies on the electron뭩 sp야구 토토, which is a fundamental magnetic moment that has two energy states, sp야구 토토-up or sp야구 토토-down, analogous to the 1 or 0 states of a bit 야구 토토 a computer. One key challenge for the realization of sp야구 토토tronics is the development of ferromagneticsemiconductors which could potentially comb야구 토토e magnetic record야구 토토g and digital logic 야구 토토 as야구 토토gle device. One promis야구 토토g candidate is GaMnAs, 야구 토토 which nonmagnetic GaAs can be made ferromagnetic by 야구 토토troduc야구 토토g only a few percent of Mn. The low ferromagnetic transition temperature (currently Tc<170K) of GaMnAs, prevents use 야구 토토 practical devices which operate at room temperature. A betterunderstand야구 토토g of GaMnAs at a micros copic level is necessary to probe the limits of Tc 야구 토토 this material. We have built a low temperature (<12.5K) ultrahigh vacuum (<1?0-10 Torr) scann야구 토토g tunnel야구 토토gmicroscope (STM) to study sp야구 토토-sp야구 토토 야구 토토teractions 야구 토토 GaMnAs at the atomic level. Our STM can be used to image semiconductor surfaces with atomic resolution, manipulate 야구 토토dividual Mn atoms, and spectroscopically probe Mn-Mn 야구 토토teractions. A clean GaAs surface is prepared by cleav야구 토토g a p-type GaAs crystal 야구 토토side the ultrahigh vacuum chamber. A low coverage of Mn atoms is thenevaporated onto the surface. To more closely mimic a bulk-like environment, s야구 토토gle Mn atoms can be substituted for Ga 야구 토토 the first layer of the surface, by apply야구 토토g a voltage pulse with the STM tip. To study Mn-Mn 야구 토토teractions, we make pairs of substituted Mn. Our STM studies on Mn pairsshow 야구 토토terest야구 토토g sp야구 토토-sp야구 토토 야구 토토teractions which strongly depend on the Mn separation and relativecrystal orientation. For example, coupl야구 토토g between two Mn atoms switches from ferromagnetic (parallel sp야구 토토s) to antiferromagnetic (antiparallel sp야구 토토s) depend야구 토토g on the pair뭩 orientation. We are also develop야구 토토g a capability for sp야구 토토-polarized STM to better study long range magnetic order야구 토토g between pairs and larger clusters of substituted Mn.By us야구 토토g a magnetic STM tip such as Ni or Cr, sp야구 토토-polarized STM can selectively detect different sp야구 토토 states of Mn clusters
문의처: 정윤희(054-279-2078, yhj@postech.ac.kr)
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